No spark?

Ok...so me being my newbie self...I'm dyin to see if there is even an attempt at starting my dad's old bike.

I cleaned the fuel tank thoroughly...doesn't appear to be anymore rust in the tank, and when I put a quart or so of gas in it and swish it around, it comes out clear. I realize the carbs still need cleaning...BUT...I gotta try.

I hooked the fuel line back up. It's in neutral, on the center stand, kickstand up, and I'm squeezing the clutch. I try to start. Engine turns, I hear the "compression", I see fuel being drawn through the inline filter, but NOTHING.

I'm guessing since I smell fuel after several attempts fuel is at least getting to the thing. But it doesn't sound like it's trying to actually fire. I found the two coils under the fuel tank and the rear of the two coils weren't mounted to the frame and the black wire was loose. Problem solved? NO. Reattached them to the frame, but still doesn't appear to be any spark.

Two questions. One...how do you actually (the RIGHT way) test for spark at the plug? I mean I know you could pull it out, leave it in the boot, touch the engine, and look for spark but I thought I read that can damage the coils or some other part. Question two, what's the backward path from coils to battery?

Or is it simple, and I'm just not starting it right?? (that'd be my luck, but that'd be a good thing since I'm trying to get it at least road worthy without much cash, I'll work on "pretty" later)

 

I was having that problem I used a multimeter on the battery it read 11.53 more than enough to turn over the motor but not enough to produce spark the guys on here were more than helpful it turned out to be the battery test the battery Good Luck

 

Thanks for the idea...have 12.72 at the battery. That should be good, shouldn't it?

 

12.72 is indicates a fully charged battery. mesaure and see what it reads while cranking. it might indicate charge but can't handle a load.

on automotive batteries. electricity ALWAYS flows from positive to negative. negative being ground. everything else in life flows from negative to positive. least that's what i was taught in trade school.

as for the actual circuit. i beleive it would be power to the pickup coils. then over to tci igniter box, then over to coils and down to the plugs. and back to ground.

my wiring schematic is small and hard to read. so others with a better schematic might chime in.

 

First off to the battery: It is possible for the battery to be strong enough to quite vigorously spin the motor yet not have enough "oomph" left to fire the ignition.

It just happened to me day before yesterday; the battery in one of my 550s was just low enough that the bike wouldn't fire, although it cranked nice and fast. Pulled and fully charged the battery and it lit right up.

Be sure the battery is fully charged, and take it to the auto parts store and have it load tested.

It's also possible that one of the components of the "safety system" is malfunctioning. (Sidestand switch, because of where it lives, is at the top of the list.) However, before going through all of those components individually, simply locate and unplug your safety relay to temporarily disable that whole system. If the bike then starts, you'll have a better idea what to chase.

Install a new set of spark plugs, you may have saturated the old ones and then they won't fire even if everything else is OK.

 

oh yeah, forgot all the safety switches tied in.

 

Test to see if your ignition coils are working properly. Robert tested mine, and one of the wires and boots were jacked up.

 

Thanks, I'll try the safety relay. I don't have the manual yet (have ordered it)...so where might I be looking for that relay? I'm also going to go ahead and replace the fuse box, I found a good article on replacing it with the spade type fuses.

 

Your coil requires one "hot" lead (+) and one negative. In automotive systems, and most bikes I've worked on, the CDI or points do their switching on the negative side of the coil...in essence turning the ground on and off, which makes the field collapse in the coil and results in a discharge through the secondary windings, into the plug wires to the spark plugs.

I haven't tried it with a bike, but on cars I'll probe the leads on the coil with a test light, look for one constant light with ignition ON, and the other should flash on-off-on-off as the engine is cranked, this is the CDI turning the coil on and off in response to the timing pulses from the pickup coil (crank trigger). So if you see no power supply to the coil, work your way back through that issue (or supply and alternate hot lead for testing, see if that gets it to start)...if no timing signal, suspect the CDI or trigger, I would think. I'm not clear on which side the safety switches figure, but I would suspect they control the hot side.

Nothing wrong with testing for spark using a plug in a boot, long as the plug is known good and properly grounded to the head...and usually even if it wasn't, it's not going to hurt the coil...what you've heard comes from modern automotive ignition, they use much higher secondary voltages and can jump to sensitive components or burn through insulators to find ground if a proper one is not supplied...not really an issue on old stuff like this...

 

PS I vaguely remember one incident where my sidestand switch gave me trouble...it would start and run but died every time I began let the clutch out...I found the switch on the underside of the bike and was going to simply shunt the wires and bypass it, but I think I noticed a plunger that wasn't moving right and a shot of WD-40 and a few minutes of soak time corrected it.

It wouldn't be a bad idea to locate any switch or switches under there and do this anyway....even if they aren't the issue, they could cause trouble later if they stick, after sitting so long.

 

Ahem...(Voice of experience here)
I will caution all, the improper grounding of the spark plug CAN damage the TCI. It is not bullet proof. While the afore mentioned statement is a generality, it does not apply to our XJs in this matter. Don't risk it. The manual cautions against it for good reason.
Other than that, good advice in troubleshooting coil firing. I just wouldn't want to be the fellow holding the test light on that secondary line. Best bet is to place the test light and set it down before energizing the circuit.

 

NO! You don't hold it on the secondary (spark) side...you're just testing for 12v constant and intermittent on the primary leads...

 

Hey where is the CDI...sorry..TCI, I gotta remember the proper letters for it here...located?

This is the only reason I can think of why it would be an issue...in case the coil was able to throw and ungrounded spark directly to it because it is mounted right next to it...secondary voltages should not be able to damage primary ignition otherwise...completely different circuits...

 

my xj didn't have 2 wires. it had 1. it was grounded to the frame.

some of the switches are actually ground circuits. when flipped, they ground out the tci. basically shorting it out. i think the kill switch is one. the rest are probably what completes the circuit.

i've never had a problem so i can't say for sure.

the only bike i did have a problem with was a 76 yamaha 500 enduro. it had magneto and points. and worked totally opposite of how a car with points worked. it was the same theory in principal. just worked differently with a different wiring layout. and the only safety device it had was kill switch that grounded out before it hit the points.

it was really a simple wiring job once i had the schematic figured out.


i've used a test light before in the seconday wiring. but not for voltage purposes. only for spark purposes. without the ground connection hooked up. real handy procedure with the cap off and not enough wire to touch ground.

 

Huh. That changes things. Not the first time I've been surprised by how Asian motorcycle circuits work...reversed positive and negative roles from what I'm used to looking at.

So in this case, the switching would have to take place on the positive side, and you should see it switching on that one when cranking.

If the coil gets its ground path from the frame, he'd better check to see that his frame ground from the battery is complete, otherwise all bets are off.

I'm still kicking this around in my head...it seems like one lead providing both coil switching AND power to the primary windings would cause a lag in coil recovery times...unless the TCI allows for this and just times the impulses along a different curve than a conventional ignition...

Damn Japanese...always gotta be different....

 

the thing i hate about motorcycles is it's all independent. 4 carbs. 2 coils. and all the little peaces that are seperate instead of like a car. you can't have an alternator. you have to have a armature, stator, rectifier, and regulator.

not looking forward to the day i have a FI bike and i have to screw around with the computer. LOL.

 

The XJ system switches the positive side. One wire to provide the input pulse of +12v with the return running back to the TCI. It doesn't take much current to step up the voltage in the coil, so we ought not to think of this ignition system in the conventional points system way. I'm horrible at circuit identification so I cannot tell you how it recovers fast enough to do what it does but my experience is that it does it really well compared to points.
The switching transistors in the TCI are rated at a couple o'hundred volts (don't have the part right here or I'd let you know particulars).
Checking the frame ground for the coils would be a great idea, easily overlooked and usually ignored.
And I'm sure many of us think certain systems work like others we are famililar with, I'm guilty of this myself. The saying goes "challenge your preconceptions or they will challenge you". I won't say a cross word about our Japanese brothers, they make a fine product.

 

Thank you, that does explain the vulnerability of the TCI as well...it makes sense to me now.

My comment about the Japanese was tongue in cheek. Yeah different. And usually better

Thanks again!

 

This type of circuitry really isn't that unusual, Detroit does it on both Ford and Chryslers.

 

In what respect? I can still diagnose DIS ignitions using the procedure I described....